The Stovebolt Site Forums The Shop Area Engine Shop 235 main bearings - later style

At first I thought my '55 235 had the later style...until I removed them from the caps and discovered the center nub on the cap side only. No center nub in the block.

Are my bearings in the easier-to-find or harder-to-find group? Nervously awaiting reply...

Skooter,

I think the question may be better answered if we know what size bearings you need. Standard, .010 undersize, etc.???

Here is a link to one of our many normal vendors that has them listed: https://store.fillingstation.com/de...5_6CYL_MAIN_BEARING_SETSPECIFY_SIZE.html

You may not know if they have them "In Stock" until you select the size you want and put them in a "cart".

Good luck in your search.

You're in luck- - - - -that's the later style bearing. The early ones had dowels on top and bottom, and used shims to adjust the clearance. The tabs on the upper bearings started in mid-year 55, IMHO, and went to 62/63. The early blocks can be modified to accept the later bearings, but then the crankshaft has to be custom ground and polished to get the right oil clearance.
Jerry

Thanks Dan. Don't know what particular size yet. Everything's headed to machine shop Monday; they'll measure, turn crank, etc then let me know. Was more concerned about what style (nubs vs. no nubs) than size at this point.

As you can see, I barely have enough knowledge to ask the right question, so you guys go easy on me!

Outstanding!! Thanks for the info. FWIW, this engine had no shims at all on rods or mains.

The engines with the locator tabs at the parting line don't use main bearing shims- - - - -only the ones with dowels top and bottom. NO insert bearing connecting rods are shimmed- - - -only Babbit bearing rods have them.
Jerry

There's a good reason for the difference in the bearing design. To change the upper bearing shell with the dowel built in, with the engine installed in the vehicle, it's necessary to lower the crankshaft nearly an inch to allow the bearing to roll out of the block. The later model bearing with the anti-rotation tab at the parting line and no dowel in the upper bearing shell can be rolled out by simply loosening all the main caps a little and putting a cotter pin into the oil hole in the crankshaft. Since the spray-oilers didn't have holes drilled in the crankshaft, the doweled mains didn't make much difference. GM also figured out that adjusting main bearing clearance with shims was not really necessary with the precision machining procedures available in the mid-1950's.
Jerry